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Trees are known to give a range of environmental benefits, but new research suggests that they are also playing an important role in saving human lives during heatwaves.

A national tree symposium at Adelaide University of Adelaide has been told their value in urban landscapes is often unappreciated.

Professor Nigel Tapper of Monash University says hundreds of people die during extreme heat in the cities in summer and trees may be keeping the temperatures a touch lower than they otherwise would be.

"One of the best ways we think that urban environments can be cooled, particularly under heatwave conditions, is by reincorporating water and vegetation back into the environment," he said.

Professor Chris Daniels of the University of South Australia agrees.

"The trees, the plants, the greenery affect climate," he said.

"They reduce the heat-island effect and in fact watering these trees has a tremendously beneficial effect with dealing with long periods of heat."

Conference official David Lawry worries that trees are under increasing threat in urban areas.

"Under the current to shift to increasing housing density, I think our urban trees are very, very much under threat," he said.

A solution being suggested to help street trees flourish is to divert rainwater from gutters directly to the trees' root zones.

A device to do that is being tested in the Unley area in Adelaide to show the benefits.

"The nature strip is in fact the driest part of the urban environment so the idea is to move this polluted, nutrient rich water from the gutter, diverting it from going into the stormwater system," David Lawry explained.

The experts explain the devices could deliver up to 400 litres of water directly to trees during moderate rain, resulting in healthier trees, more comfortable urban environments and less stormwater getting to waterways and the sea.